@Nobbie:
More information required.
Are the G729 extensions at the same location as the GSM ones?
Are the ports forwarded to the PBX on that network?
Are the G729 extensions able to register?
Are you able to make any calls successfully at all then lose two-way communication after a certain number of minutes?
P.S. Did you make sure you have UDP ports forwarded and not TCP?
Other thing, now is not only with g729…
All that you say are ok but i had to make some capture on the PBX and i can see the problem though that is too rarely, because i can see the extension registered with the wan ip but the traffic rtp is through private ip.
I have a simetric dsl with a static ip but the others places have a adsl connections to internet, they have nat configured on the routers, i tried to open all of ports and create a dmz but anything.
I made others test with a client sip by internet on a cell phone and works ok but in adsl or cable modem not work.
My configuration in pfsense
My LAN is 10.10.0.0/24
WAN 201.204.13.xx
i already open 5060 (sip) udp, 10000 - 20000 udp (rpt)
I see in the PBX
Sip registered with the wan ip 201.203.xxx.xxx but rtp through 192.168.1.2 (This is the private network configured in the adsl)
why i see the private ip on the wan interface? and why my elastix registered the extension with the public ip and send the traffic rtp through the private network?